Hi, yep in level 4 you choose your own music and have your own routine in australia. basically there are required elements you your coach will make up a routine around these elements.
They are pretty basic in level 4,
Your routine must contain 2 tumble runs. 1 is a cartwheel, cartwheel series. and the other 1 is a round off
You also need either a back walkover, a front walkover, a tic toc or a backward roll to front support. Just one of those
A full turn on 1 foot
A jump full turn
and a leap series with 2 180 degree split leaps.
I'm not sure how it works in your state but then there are bonus skills like a front handspring instead of the cartwheel cartwheel but most states dont do that for state levels.
For your music it needs to be any piece with no words. Usually for level 4 you want it to be about a minute to a minute and 10 seconds long.
If you have trouble finding something you like why not ask your coach. They will probably have lots of pieces you can listen too and choose from.